Got a question from a customer on how to move there blob storage assets from Azure Commercial to Azure Government. The easiest way is via AzCopy: http://aka.ms/AzCopy, but you have two options.

Technique #1: Server-side copy

Even though the public cloud and the government cloud are on separate networks the server-side copy routine works like a champ. Server-side copy will schedule a job running on the Azure backbone that will move the files using “spare bandwidth capacity”.

If you need more control then consider setting up a “jump” VM. Using this technique you can “reserve” capacity, by purchasing VM’s to do the copy. While this requires a bit more work, this will allow you to scale your copy server(s) to whatever level you need to meet your needs, an IaaS VM with AzCopy would work great for this, or you can write something more complex using PaaS WorkerRoles. The basic idea is to copy the files down to the local disk on the VM then back up to blob storage on the other end.
BTW: If you need extra local disk to do the transfer try setting up storage spaces, more info here:
http://blogs.technet.com/b/keithmayer/archive/2013/01/24/step-by-step-building-a-windows-server-2012-storage-server-in-the-cloud-with-windows-azure.aspx

Regardless of what technique you select, you will be responsible for any egress charges moving data between two different datacenters.